A layer system of this type has a substrate comprising a metal alloy based on nickel, cobalt or iron. Products of this type are used in particular as components of a gas turbine, in particular as gas turbine blades or vanes or heat shields. The components are exposed to a hot-gas stream of aggressive combustion gases, and consequently they have to be able to withstand high thermal stresses. Furthermore, it is necessary for these components to be resistant to oxidation and corrosion. Furthermore, mechanical demands are imposed in particular on moving components, for example gas turbine blades or vanes, but also on static parts. The power and efficiency of a gas turbine in which components that can be exposed to hot gases are used rise with an increasing operating temperature. To achieve a high efficiency and a high power, components of the gas turbines which are subject to particularly high stresses from the high temperatures are coated with a ceramic material. This ceramic material acts as a thermal barrier coating between the hot-gas stream and the metallic substrate.
The metallic base body is protected from the aggressive hot-gas stream by coatings. Modern components generally have a plurality of coatings which each perform specific tasks. Therefore, a multilayer system is present.
Since power and efficiency of gas turbines rise with increasing operating temperature, constant attempts have been made to achieve a higher gas turbine performance by improving the coating system.
EP 0 944 746 B1 discloses the use of pyrochlores as thermal barrier coating.
However, to be used as material for a thermal barrier coating, it is necessary for materials not only to have good thermal barrier properties but also good bonding to the substrate.
EP 0 992 603 A1 discloses a thermal barrier coating system comprising gadolinium oxide and zirconium oxide, which is not supposed to have a pyrochlore structure.